Function Of Plasma Membrane In Prokaryotic Cell – The cell theory states that the cell is the basic unit of life. However, cells vary considerably in size, shape, structure, and function. At the simplest level of construction, all cells have a few basic components. These include the cytoplasm (a gel-like substance composed of water and dissolved chemicals necessary for growth) contained within the plasma membrane (also called the cell membrane or cytoplasmic membrane); one or more chromosomes that contain the genetic blueprint of a cell; and ribosomes, organelles used to make proteins.

Beyond these basic components, cells can vary greatly between organisms and even within the same multicellular organism. The two largest categories of cells, prokaryotic cells and eukaryotic cells, are defined by several key differences in cell structures. Prokaryotic cells do not have a nucleus surrounded by a complex nuclear membrane and generally have a single circular chromosome located in the nucleoid. Eukaryotic cells have a nucleus surrounded by a complex nuclear membrane that contains many rod-shaped chromosomes.[1]

Function Of Plasma Membrane In Prokaryotic Cell

All plant and animal cells are eukaryotic. Some microorganisms are made of prokaryotic cells, while others are made of eukaryotic cells. Prokaryotic microorganisms are classified under the domains Archaea and Bacteria, while eukaryotic organisms are classified under the domain Eukarya.

Plasma Membrane (cell Membrane)

Structures inside a cell are similar to organs inside the human body, with unique structures suited to specific functions. Some structures found in prokaryotic cells are similar to those found in some eukaryotic cells; others are specific to prokaryotes. Although there are some exceptions, eukaryotic cells tend to be larger than prokaryotic cells. The relatively larger size of eukaryotic cells dictates the need to compartmentalize different chemical processes in different areas of the cell using complex membrane-bound organelles. In contrast, prokaryotic cells generally lack membrane-bound organelles; however, they often contain inclusions that compartmentalize their cytoplasm. Figure 2.10 depicts structures commonly associated with prokaryotic cells. These structures are described in more detail in the next section.

Figure 2.10 A typical prokaryotic cell contains a cell membrane, chromosomal DNA concentrated in a nucleoid, ribosomes, and a cell wall. Some prokaryotic cells may also have flagella, pilin, fimbriae, and a capsule.

Individual cells of a particular prokaryotic organism are usually similar in shape or cell morphology. Although thousands of prokaryotic organisms have been identified, only a few types of cell morphology are commonly seen under a microscope. Figure 2.11 names and illustrates cell morphologies commonly found in prokaryotic cells.

Figure 2.11 (Coccus micrograph credit: Janice Haney Carr’s Work Change, Centers for Disease Control and Prevention; Coccobacillus micrograph: Janice Carr’s Work Change, Centers for Disease Control; Spirochete micrograph credit: Centers for Disease Control and Prevention’s Work the change.

Solved 1. Identify Each Of The Structures On A Diagram Of

All cellular life has a DNA genome organized into one or more chromosomes. Prokaryotic chromosomes are usually circular, haploid (unpaired), and not bound by a complex nuclear membrane. Prokaryotic DNA and DNA-associated proteins are concentrated in the nucleoid region of the cell (Figure 2.12). In general, prokaryotic DNA interacts with nucleoid-associated proteins (NAPs), which aid in chromosome organization and packaging. In bacteria, NAPs act like histones, which are DNA-organizing proteins found in eukaryotic cells. In archaea, the nucleoid is organized either by NAPs or by histone-like DNA organizing proteins.

Figure 2.12 The nucleoid region (the area enclosed by the green dashed line) is a condensed region of DNA found in prokaryotic cells. Because of the density of the area, it does not stain easily and appears lighter in color when viewed under a transmission electron microscope.

Prokaryotic cells can also contain extrachromosomal DNA, or DNA that is not part of a chromosome. This extrachromosomal DNA is found in plasmids, which are small, circular, double-stranded DNA molecules. Cells that have plasmids often have hundreds of them in a single cell. Plasmids are more common in bacteria; however, plasmids have been found in archaea and eukaryotic organisms. Plasmids often carry genes that confer useful properties such as antibiotic resistance; therefore, they are essential for the survival of the organism.

All cellular life synthesizes proteins, and organisms in all three domains of life have ribosomes, the structures responsible for protein synthesis. However, ribosomes in each of the three domains are structurally different. Ribosomes themselves are made of proteins together with ribosomal RNA (rRNA). Prokaryotic ribosomes are found in the cytoplasm. They are called 70S ribosomes because they are 70S in size (Figure 2.13), whereas eukaryotic cytoplasmic ribosomes are 80S in size. (S stands for Svedberg unit, a measure of deposition in ultracentrifugation based on the size, shape, and surface quality of the structure being analyzed). Although they are the same size, bacterial and archaeal ribosomes have different proteins and rRNA molecules, and the archaeal versions are more similar to their eukaryotic counterparts than those found in bacteria.

What Is The Structure Of A Prokaryotic Cell?

Figure 2.13 Prokaryotic ribosomes (70S) are composed of two subunits, 30S (small subunit) and 50S (large subunit), each composed of protein and rRNA components.

Bacterial cells are usually thought of as vegetative cells, but some genera of bacteria have the ability to form endospores, structures that essentially protect the bacterial genome in a dormant state when environmental conditions are unfavorable. Endospores (not to be confused with the reproductive spores formed by fungi) allow some bacterial cells to survive long periods without food or water, as well as exposure to chemicals, extreme temperatures, and even radiation. Table 2.1 compares the characteristics of vegetative cells and endospores.

The process by which vegetative cells develop into an endospore is called sporulation, and it usually begins when nutrients are depleted or environmental conditions otherwise become unfavorable (Figure 2.14). The process begins with the formation of a septum in the vegetative bacterial cell. The septum divides the cell asymmetrically, separating the DNA protospore from the mother cell. The forespore, which will form the endospore nucleus, is essentially a copy of the cell’s chromosomes and is separated from the parent cell by a second membrane. A coat gradually forms around the protospore, placing layers of calcium and dipicolinic acid between the membranes. A protein spore coat then forms around the shell while the mother cell’s DNA degrades. Further maturation of the endospore occurs with the formation of the outermost exosporium. The endospore is released after the mother cell breaks down, completing sporulation.

Figure 2.14 (a) Sporulation begins after asymmetric cell division. The pro-spore is surrounded by a double layer of membrane, a coat, and a protein spore coat until the mother cell breaks down and is released as a mature endospore. (b) Electron micrograph of a

Structure Of Prokaryotic Cells (a Level Biology)

Cells undergo sporulation. Endospores are visualized using malachite green spore stain. (Credit b: work modification by Jonathan Eisen)

Endospores of some species have been shown to remain dormant for long periods of time, up to thousands of years [2]. However, when living conditions improve, the endospores undergo germination, re-entering the vegetative state. After germination, the cell becomes metabolically active again and is able to carry out all its normal functions, including growth and cell division.

Not all bacteria have the ability to form endospores. However, there are a number of clinically significant endospore-forming Gram-positive bacteria

. Fighting such pathogens is particularly difficult because their endospores are very difficult to kill.

Functional Anatomy Of Prokaryotic Cells Flashcards

The structures that enclose the cytoplasm and internal structures of the cell are known as the cell envelope. In prokaryotic cells, cell envelope structures vary depending on the type of cell and organism. Most (but not all) prokaryotic cells have a cell wall, but the composition of this cell wall varies. All cells (prokaryotes and eukaryotes) have a plasma membrane (also called cytoplasmic membrane or cell membrane) that exhibits selective permeability, allowing some molecules to enter or leave the cell while restricting the passage of others.

The structure of the plasma membrane is often described by the fluid mosaic model, which refers to the ability of membrane components to move fluidly in the plane of the membrane, as well as the mosaic composition of the components, which include: a diverse array of lipid and protein components (Figure 2.15). The structure of the plasma membrane of most bacterial and eukaryotic cells is bilayered, consisting mainly of phospholipids formed by ester bonds and proteins. These phospholipids and proteins can move within the plane of the lateral membranes as well as between two phospholipid layers.

Figure 2.15 The bacterial plasma membrane is a phospholipid bilayer with a number of embedded proteins that perform various functions for the cell. Note the presence of glycoproteins and glycolipids, the carbohydrate components of which protrude from the cell surface. The abundance and arrangement of these proteins and lipids can vary greatly between species.

Archaeal membranes differ fundamentally from bacterial and eukaryotic membranes in several significant ways. First, archaeal membrane phospholipids are formed by ether linkages, unlike the ester linkages found in bacterial or eukaryotic cell membranes. Second, archaeal phospholipids have branched chains, whereas bacterial and eukaryotic cells are straight chained. Finally, although some archaeal membranes can be formed from bilayers

What Is A Prokaryotic Cell?

Function of plasma membrane in plant cell, function of plasma membrane in a cell, major function of plasma membrane, plasma membrane in cell, plasma membrane animal cell function, cholesterol in plasma membrane function, prokaryotic cell plasma membrane, plasma membrane cell function, plant cell plasma membrane function, function of plasma cell membrane, bacterial plasma membrane function, glycoprotein function in plasma membrane